The ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(α${,}^2$He${)}^{210}$Pb reaction has been investigated at about 55 MeV incident energy. The angular distributions of prominent transitions were analyzed with the distorted-wave Born approximation. At low excitation energies, states built on 2${\mathit{g}}_{9/2}$ single-particle strength are found, while at higher energies configurations including 1${\mathit{j}}_{15/2}$ strength dominate. Together with the predictions of the crude shell model the main configurations of most observed transitions were identified. The results are compared to shell-model calculations with the Kuo-Herling residual interaction modified by Warburton and Brown.

Neutron total cross sections for ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ have been measured with good statistics (∼1%) and good energy resolution over the energy range 4≤${\mathit{E}}_{\mathit{n}}$≤20 MeV. Two techniques have been used to infer the level density of the compound nuclei. The first is the conventional procedure of deducing an average level width and relating this to the level density. An alternative method is to deduce the level density from the magnitude of the variance of the cross section. A previous study of these two techniques suggested that the two yielded results which were not completely consistent. Our examination of the discrepancies indicates that they are reduced but not eliminated with better data. It seems likely that a part of the problem is the uncertainty in input parameters.

The multipole mixing ratios of γ-ray transitions between low-lying states in ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ were determined by measuring γ-ray anisotropies from oriented ${}_{}{}^{71}{}_{}{}^{}\mathrm{As}$ nuclei. Nuclear orientation of ${}_{}{}^{71}{}_{}{}^{}\mathit{Fe}$ samples occurred through the magnetic hyperfine interaction at 5 mK. The interacting boson-fermion model was used to calculate transition matrix elements and, in general, there is good agreement between experimental results and theoretical values of E2:M1 multipole mixing ratios.

The cross sections for populating the $2_1^{+}$, $3_1^{\mathrm{-}}$, and $5_1^{\mathrm{-}}$ states of ${}_{}{}^{146,148}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ have been determined by inelastic scattering of 26 MeV protons and analyzed using coupled-channels calculations. In these nuclei, the $5_1^{\mathrm{-}}$ states are usually considered to be ‘‘octupole coupled’’ states arising from the coupling of the $2_1^{+}$ and $3_1^{\mathrm{-}}$ states. It is found that the differential cross sections for excitation of the $5_1^{\mathrm{-}}$ states are somewhat larger than would be expected for octupole coupled structure. This excess strength can be explained in terms of small admixtures of two quasiparticle excitations in the $5_1^{\mathrm{-}}$ states.

Data were measured for pion double charge exchange on ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ at ${\mathit{T}}_{\mathrm{\pi }}$=400 MeV and three laboratory angles: 0°, 10°, 20°. Angular distributions were measured for the double isobaric analog state, the analog of the giant dipole resonance, and the giant dipole built upon itself. The excitation function of each of these resonances is discussed. Evidence is found for separate ${\mathit{J}}^{\mathrm{\pi }}$ components of the double dipole resonance, and cross sections of these components are extracted.

Neutron and proton bound states and Gamow resonances (Berggren representation) are used as single-particle states to calculate random-phase approximation (RPA) particle-hole multipole excitations in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and vertex functions for the coupling between particles and multipole vibrations. Escape widths, corresponding to low-lying one-proton states in the neighborhood of the Z=82 shell, are calculated in the framework of the standard particle-vibration coupling model. It is shown that the inclusion of Gamow resonances in the single-particle basis and in the RPA wave functions does not affect the dominant one-particle character of low-lying states of the renormalized spectrum corresponding to the odd-even system, as predicted by the particle-vibration coupling model. This result shows that the Berggren representation is suitable to deal with the particle-vibration coupling mechanism and that it can be applied to the study of high-lying single-particle states as well.

Thermal and quantal fluctuations are included in the partition function of the pairing and quadrupole model. The formalism is applied to the calculation of the thermal response functions. The effects of both thermal and quantal fluctuations to the level densities are studied. The limits and the physical content of the scheme are analyzed.

We study interactions of a proton impurity with density oscillations of the neutron matter in a Debye approximation. The proton-phonon coupling is of the deformation-potential type at long wavelengths. It is weak at low density and increases with the neutron matter density. We calculate the proton’s effective mass perturbatively for a weak coupling, and use a canonical transformation technique for stronger couplings. The proton’s effective mass grows significantly with density, and at higher densities the proton impurity can be localized. This behavior is similar to that of the polaron in solids. We obtain properties of the localized proton in the strong-coupling regime from variational calculations, treating the neutron matter in the Thomas-Fermi approximation.

On the basis of a simple S-matrix model we show that, at high average level density, local fluctuations in the density of states of an open quantum mechanical system create locally a few broad resonance states together with a larger number of narrow (trapped) ones. The widths of the broad states are of the order of the length which characterizes the local fluctuations in the spectrum. They serve as a background for the narrow ‘‘fine-structure resonances.’’ If the spectrum shows a hierarchical fluctuation pattern in energy, this behavior repeats on all energy scales. From these results, we conjecture that the well-known intermediate structures in nuclei at high level density, described by the doorway mechanism, are formed due to such a trapping effect.

A relativistic energy density functional is constructed to investigate the Dirac effects on different properties of the structure and scattering of finite nuclei. The kinetic energy density has been derived within a relativistic extended Thomas-Fermi model and includes gradient corrections to second order in ħ. The effective mass and the volume term of the potential energy density have been obtained from a local density approximation to Dirac-Brueckner calculations of nuclear matter carried out with a realistic nucleon-nucleon interaction. This volume term is supplemented by the Coulomb energy and by conventional phenomenological surface and symmetry terms, and the few free parameters of the functional are suitably adjusted. Attention is then focused on the calculation of fission barriers of rotating nuclei and of the complex optical potential for heavy ion collisions at intermediate energies. It turns out that the effects of the density-dependent Dirac spinor which have been incorporated in this approach allow for a reasonable description of the investigated properties.

The spontaneous fission decay of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ has been analyzed in a statistical model with emphasis on describing recently reported high energy γ-ray spectra. An enhanced γ emission in the range from 3 to 10 MeV which is observed for nearly symmetric mass splits is readily understood as a result of the different fragment excitation energies. The model includes a viscous motion to the scission point with the possibility of prescission γ emission. It was found that even with saddle-to-scission times of ${\mathrm{\tau }}_{\mathrm{sc}}$<66×${10}^{\mathrm{-}19}$ s, the maximum consistent with prescission neutron multiplicities, prescission γ rays are overwhelmed by fragment γ rays. Thus, the recently reported strong angular anisotropy of γ rays in the range ${\mathit{E}}_{\gamma }$=8–12 MeV is unexplained within the present understanding of the fission process.

Using the corpus of data on the (γ,p), (γ,n), (γ,2n), and (γ,${\mathit{n}}_0$) cross sections of nine light nuclei ${(}^{13}$C, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$), the ${\mathit{T}}_{>}$ and ${\mathit{T}}_{<}$ isospin components of the giant dipole resonance have been separated. The relative strengths of these components have been extracted, together with the energy differences between the centroids of the components. The ratio of the ${\mathit{T}}_{>}$ energy-weighted integrated cross section to the total cross section is somewhat better represented by the simple geometric factor 1/(${\mathit{T}}_0$+1), where ${\mathit{T}}_0$ is the isospin of the ground state of the excited nucleus, than by a more complete expression which takes into account dynamical effects. If the energy difference between the centroids is represented by ${\mathit{U}}^{\mathrm{*}}$(${\mathit{T}}_0$+1)/A, the average value of ${\mathit{U}}^{\mathrm{*}}$ for the three p shell nuclei is found to be 57 MeV, while that for the six s-d shell nuclei is 93 MeV.

Different aspects of scaled factorial moment analysis have been performed with the pion data of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Ag/Br interactions at 2.1 GeV/nucleon with the objective of understanding the intermittency effect and its dependence on experimental parameters e.g., incident energy, phase space variable of analysis–its dimension and window size, multiplicity in the window. An overview of analyses carried out, so far, motivates the study. The phase space variable and multiplicity dependences of intermittency have been studied. While compared with other available higher energy data in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Ag/Br interactions, the energy dependence of intermittency, though indicative, could not be concluded due to inconsistent values of intermittency exponents in higher energy data of the same projectile-target analyzed by different groups.

The ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$(p→,α${)}^{206}$Pb reaction has been studied at an incident proton energy of 22 MeV using a polarized proton source and a quadrupole-dipole-dipole-dipole spectrometer. The differential cross sections and asymmetries for transitions to levels of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ up to an excitation energy of 5.333 MeV have been measured. Evidence for the presence of multiplets of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ states homologous to the parent ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ states is discussed. The differential cross sections and asymmetries for the transitions to these homologous states are interpreted in terms of the experimental differential cross sections and asymmetries of the parent states as well as by theoretical calculations using both conventional Woods-Saxon and double-folded α-particle potentials. The differential cross sections and asymmetries for the low-energy states of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ which involve the pickup of the ${\mathit{h}}_{9/2}$ proton outside the closed shell are analyzed.

High-resolution neutron cross section measurements for ${}_{}{}^{58}{}_{}{}^{}\mathrm{enriched}$ targets were made at the Oak Ridge Electron Linear Accelerator of transmission below 20 MeV, of differential elastic scattering from 10 keV to 5 MeV, and of capture from 2.6 keV to 2.5 MeV. The transmission data were analyzed from 0.1 to 813 keV with a multilevel R-matrix code which uses Bayes’ theorem for the fitting process. This code provides energies and neutron widths of resonances within the analyzed region, as well as a possible parametrization for resonances external to that region, as a way of describing the smooth cross section over the entire energy range. The differential elastic data at different scattering angles were compared to theoretical calculations from 30 to 813 keV using an R-function code which is based on the Blatt-Biedenharn formalism. Various combinations of spin and parity were tested to predict cross sections for the well-defined l>0 resonances, and comparison with the data then provided spin and parity assignments for most of these resonances.

The capture data were analyzed from 5 to 450 keV with a least-squares fitting code using the Breit-Wigner formula. The resulting set of resonance parameters yields values for the thermal total and capture cross sections within experimental uncertainties. A total of 482 resonances are reported, of which five are fictitious s-wave resonances outside the analyzed energy region and 61 are seen and analyzed only in the capture data. The reduced widths of the 61 s-wave resonances follow the Porter-Thomas distribution and their nearest neighbor spacings agree with the Wigner distribution. The average s-wave level spacing is 13.1±0.9 keV and the s-wave strength function is (3.2±0.6)×${10}^{\mathrm{-}4}$. Since most of the large non-s-wave resonances have their angular momentum assigned with confidence, the strength functions for the p- and d-wave resonances could be determined; values are (1.3±0.2)×${10}^{\mathrm{-}4}$ and (3.0±0.4)×${10}^{\mathrm{-}4}$, respectively. The level densities calculated with the Fermi-gas model for l=0 and l>0 resonances are compared with the cumulative number of observed resonances. The average radiation widths were deduced from resonances analyzed in the three data sets below 450 keV. The mean values and standard deviations of the distributions of the radiation widths are 2.3±1.7 eV for the s-wave resonances, 0.77±0.32 eV for the p-wave resonances, and 1.4±0.5 eV for the d-wave resonances. The average capture cross section as a function of the incident neutron energy is compared to a prediction based on the tail of the giant electric dipole resonance.

Inclusive and semiexclusive elemental production cross sections of projectilelike fragments emerging in the collision ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{238}$U at 110.4 MeV have been investigated. Energy spectra and angular distributions of projectile residues with charge from Z=3 to Z=8 have been measured. It has been found that, as expected, the dominant reaction mechanism in the peripheral collisions is a mass transfer from projectile to target mainly dominated by a transfer of an α particle. The in-plane coincidences between projectilelike and fission fragments suggest that 14% of the total fission cross section is associated with the fission of a targetlike nucleus.

We have measured the branching ratios ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,p${)}^3$H${/}^2$H(d,n${)}^3$He, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(d,p${)}^7$Li${/}^6$Li(d,α${)}^4$He, and ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$(d,p${)}^{11}$B${/}^{10}$B(d,α${)}^8$Be between c.m. energies of 3 and 15 keV, 20 and 135 keV, and 58 and 142 keV, respectively. Our measurements of the ${}_{}{}^2{}_{}{}^{}\mathit{d}$ reaction are in good agreement with R-matrix calculations of the branching ratio. We find no enhancement of the (d,p) branches of these reactions at the lowest observed energies. Implications of our findings to recent claims of anomalous production of heat from deuterium-metal systems are presented.

Inclusive ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${\mathrm{\pi }}^{+}$,p) and exclusive ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${\mathrm{\pi }}^{+}$,2p) data are presented for 115 MeV and 165 MeV pions. Using a combination of distorted-wave impulse approximation (DWIA) calculations for two-nucleon absorption and phase space simulations for more complicated processes, the data are fit and the total direct two-nucleon absorption cross sections are extracted. These cross sections fall faster with energy than ${\mathrm{\pi }}^{+}$d→pp. The DWIA calculations were used to calculate the effects of final state interactions (FSI). After correcting for FSI, the two-nucleon absorption process is found to dominate at 115 MeV, becoming less important as the incident energy increases to 165 MeV. The decrease with energy in the two-nucleon fraction of the total absorption cross section is found to be in remarkably good agreement with theoretical predictions.

High-lying single-particle and single-hole states were studied using ${(}^7$Li${,}^6$Li), ${(}^7$Li${,}^6$He), ${(}^{12}$C${,}^{13}$C), and ${(}^{12}$C${,}^{13}$N) reactions at 30 MeV/nucleon on the targets ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$. Broad resonancelike features were observed in both proton and neutron transfer reactions at excitation energies close to the excitation energies of the giant quadrupole resonances. The measured excitation energies and reaction Q values suggest that these features are predominantly single-particle states rather than collective giant resonance excitations. The existence of an extra particle or hole outside closed-shell nuclei does not change the strengths of the broad peaks significantly, but does change the excitation energies in some cases. Shell model calculations in the Pb region support this conclusion.

The absolute cross section and angular distributions for γ-ray production in the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{\mathrm{nat}}$Ag at 35 MeV/nucleon have been measured. Calculations of the expected γ-ray yield using an enhanced version of the nucleon exchange transport model have been performed. It has been observed that use of a sharp ground state momentum distribution in the γ-ray calculations does not lead to reproduction of the experimental yields. Diffuse momentum distributions have been incorporated into the model, and the calculations with these momentum distributions give good agreement with experimental yields. Similar calculations have been performed for the production of preequilibrium neutrons and protons for the same system.